X hits on this document





2 / 10

manufacturing.3 These manufacturing advantages can create low-cost, pervasive

electronic applications such as flexible displays and RFID tags. However, the mobility of

organic semiconductor cannot match the performance of field-effect transistors based on

single-crystalline inorganic semiconductor such as silicon or germanium. These inorganic

semiconductors have charge carrier mobilities nearly three order of magnitude higher

than typical organic semiconductor. 3 As a result of this limitation, organic

semiconductors are not suitable for use in electronic applications that require very high

switching speeds. However, the performance of some organic semiconductors, coupled

with their ease of processing makes it competitive in electronic applications that do not

require high switching speed such as amorphous silicon used for TFT-LCD.

Main Body:

Organics semiconductors are possible because carbon atoms can form sp2-

hybridisations where the sp2-orbitals form within a plane and the pz orbitals are in the

plane perpendicular to it. 4 For organic molecules, a σ -bond between two carbons are

formed by creating an orbital overlap of two sp2-orbitals (Figure 1). This creates a large

energy difference between the occupied binding orbitals and the unoccupied anti-binding

orbitals. This large energy difference leads to insulating properties, and thus longer

chains of carbon atoms would have a larger gap between the highest occupied molecular

orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). However, in sp2-

hybridisation, the pz orbitals form additional π -bonds. These bonds have much smaller

energetic difference between the HOMO and LUMO, leading to semiconducting


Document info
Document views29
Page views31
Page last viewedWed Oct 26 10:04:09 UTC 2016